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Major Party Index Data

In order to measure the strength of the parties in each state, the Major Party Index (MPI) was built by averaging the results of the six major elections that take place in the fifty states. This index allows us to describe the absolute and comparative partisan leaning of each state in each election and identify trends of party strength over time within individual states, among regions, and within the nation as a whole.

MPI Data by Year

2010 update

2008
2006
2004
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970

Related Resources

For an overview of the Major Party Index, see:
James W. Ceaser and Robert P. Saldin, "A New Measure of Party Strength," Political Research Quarterly, 58:2 (June, 2005): 245-256. For a specific description of the various components of the MPI and the coding rules used for the 2006 and 2008 updates, see especially pp. 247-248 of the article.



For an extension of the MPI back to 1970 and a recent application, see:
John Dinan and Jac Heckelman, "Convergence and Divergence in State Political Behavior, 1970-2004," The Social Science Journal 47 (2010): 689-698. For a specific description of the coding rules used for the 1970-2004 data, see especially pp. 692-693 of the article.